1. Field of the Invention
The present invention relates generally to a Hard Disk Drive (HDD) Carrier mechanism and more specifically to Self Actuating Electro-Magnetic Conduction (EMC) Springs on the HDD Carrier Mechanism.
2. Description of the Related Art
The passage of electronic currents through electronic computing devices produces electromagnetic radiation. This electromagnetic radiation can interfere with transmissions on frequencies used for television, cell phones, and other communication devices. Therefore, regulatory agencies, such as the Federal Communications Commission and the International Special Committee on Radio Interference (Comite Internationale Special Pretrubation Radioelectrique), specify requirements for manufacturers of electronic computing devices to provide shielding for the electromagnetic radiation.
Requirements regarding electromagnetic interference, electrostatic discharges, and electromagnetic radiation are referred to as Electro-Magnetic Conduction (EMC) requirements. For a single electronic computing device, EMC requirements can be met by surrounding the single device with an electrically grounded shield. Surrounding a device with an electrically grounded shield is relatively simple when designing a single device; however, the task of meeting EMC requirements becomes much more difficult when dealing with multiple electronic computing devices.
A particular problem in meeting EMC requirements with multiple electronic computing devices involves design of the hard disk drives (HDD) forming part of an array and of the carriers by which the HDDs are inserted or extracted from an array housing. A carrier is a tray that holds an HDD and is used to insert the HDD into the array housing and to extract the HDD from the array housing. Currently, EMC shields are provided, in part, by the carrier. Each carrier's EMC shield must link with the EMC shields of adjacent carriers to form a continuous EMC shield in the array housing.
One type of EMC shield for carriers links with the EMC shields of adjacent carriers through spring biased contacts that engage the spring biased contacts of adjacent carriers. When spring biased contacts provide the EMC shield continuity, problems arise when removing a carrier from the array housing when the carriers above and below contain HDDs. One problem is that the stiffness of many current spring biased contact designs require a substantial force for the insertion of a carrier into the array housing. A typical spring biased contact has a profile similar to a tent, with contact between two spring biased contacts being made where their peaks meet in a point or a linear contact. When point or linear contacts are relied upon, the forces exerted by the spring biased contacts must be high enough to ensure electrical continuity. When these carriers are installed into array housings, their stiff spring biased contacts may scrape forcefully along the bottom of an HDD in an adjacent carrier, stripping off components or damaging the springs themselves.
Another problem involves electrical shorting. It is desirable to insert and extract HDDs while an array is operational. Removing an HDD while the array is operational is called hot plugging HDDs. The practice is also referred to as hot swapping (the terms are interchangeable). Hot plugging is necessary in systems where down time must be avoided and where it is necessary to replace a faulty HDD, to upgrade an HDD with a faster or larger disk, or simply to insert an HDD into an empty carrier as storage requirements increase. Hot plugging means that HDDs can be inserted and removed while the HDD array is operational. HDD carriers designed for hot plugging are referred to as hot plug carriers. When hot plugging an HDD using carriers with spring biased contacts, electrical shorting can occur.
Electrical shorting occurs when a spring biased contact on one carrier contacts another an HDD in another carrier. In particular, shorting can occur when a spring biased contact on one carrier contacts a capacitor on an HDD in an adjacent carrier. Thus, when designing a system that allows removal of an HDD from the array enclosure while other HDDs are running in the array, the problem of electrical shorting must be addressed.
To prevent damage to an HDD and to prevent electrical shorting, designers add bottom component insulators to HDDs. Bottom component insulators are essentially covers that protect susceptible components. Comprised of metal, metal and plastic, or just plastic, the bottom component insulators take up space. When designing an array, HDD thickness affects the vertical capacity of the array, and therefore, it is desirable to make the HDDs as thin as possible. One way to make the HDDs thinner is to avoid the necessity for bottom component insulators. In addition, bottom component insulators hinder air flow around and through the HDD. Bottom component insulators, even when perforated, may significantly affect the operating temperature of the HDDs, and an increase in the operating temperature of the HDD causes a degradation of long term reliability of the HDD. Thus, bottom component insulators affect design optimization of the cooling capacity of the array housing.
Bottom component insulators cannot be eliminated from an array using carriers with spring biased contacts unless a solution is found to the problems of damage to adjacent HDDs and to electrical shorting. Therefore, a need exists for spring biased contacts that will not contact HDDs in adjacent carriers. In particular, a carrier is needed that will allow insertion or extraction of a carrier without shorting of a capacitor component on an HDD in an adjacent carrier in the rack.